The present invention relates in general to intake manifolds for combustion engines, and, more specifically, to apparatus for introducing secondary gases into the main fuel/air mixture passing through the intake manifold.
Intake manifolds for internal combustion engine are commonly formed out of a polymeric material. In an effort to reduce noise radiating from the surface of the intake manifold due to resonant frequencies set up at particular engine speeds, it is known to provide internal and external bracing on the surface of the manifold and to provide internal posts formed out of the parent material. The internal posts traverse through the plenum cavity within the manifold, and are typical formed as indentations in upper and lower shell members. Each indentation penetrates the plenum cavity with a tunnel wall and a terminus wall. The terminus walls of the upper and lower shell members are friction welded together at the same time that outer flanges of the shell members are welded together.
Any internal structure, such as the posts, may reduce the flow area within the intake manifold which can limit the peak power of the engine. It may be possible to increase the size of the intake manifold to overcome the drop in flow area due to internal structures, but with a corresponding increase in overall size of the manifold which increases cost and weight and complicates packaging.
One additional internal structure may include features for introducing secondary gases into the intake manifold for distribution to the engine cylinders. Secondary gas sources may include an exhaust gas recirculation (EGR) system, a positive crankcase ventilation (PCV) system, and a fuel tank vapor recovery system. Ports (including tubes and injection channels) may obstruct or disrupt air flow within the manifold, especially when several such ports are deployed. Furthermore, limited space availability can result in attempting to locate ports in cramped spots which makes attachment to external devices difficult or results in interference with other components attached to the manifold.